While optimizing my deck, I'd like to hear from people who has experience in using Lion's Eye Diamond.
It's potential to cast Lattice or activate Grindstone is hard to overestimate.
I can also imagine dumping my hand while Karn grabs Ensnaring Bridge to cast it immediatelly...

...but how important that card is, because I don't see it in every build?
How many copies would you reccomend in MD and SB?
Is it crucial for fast combo win?